Radio Link Monitoring Using Downlink Control and Data Decoding Performance Characteristics

ABSTRACT

This disclosure relates to radio link monitoring techniques. According to some embodiments, a wireless device may establish a radio link with a cellular base station according to a radio access technology. The base station may provide reference signals, control signals, and data signals to the wireless device via the radio link. The wireless device may perform radio link monitoring of the radio link using characteristics of decoding performance for one or more of the control signals and the data signals. Performing radio link monitoring of the radio link may include determining whether the radio link is in-sync or out-of-sync and determining whether radio link failure has occurred.

PRIORITY INFORMATION

This application is a continuation of U.S. patent application Ser. No.15/476,632, entitled “Radio Link Monitoring Using Downlink Control andData Decoding Performance Characteristics,” filed Mar. 31, 2017, whichclaims priority to U.S. provisional patent application Ser. No.62/327,858, entitled “Radio Link Monitoring (RLM) for NW-AssistedCoverage-Constrained UEs,” filed Apr. 26, 2016, and to U.S. provisionalpatent application Ser. No. 62/332,764, entitled “Radio Link MonitoringUsing Downlink Control and Data Decoding Performance Characteristics,”filed May 6, 2016, which are all hereby incorporated by reference intheir entirety as though fully and completely set forth herein.

The claims in the instant application are different than those of theparent application or other related applications. The Applicanttherefore rescinds any disclaimer of claim scope made in the parentapplication or any predecessor application in relation to the instantapplication. The Examiner is therefore advised that any such previousdisclaimer and the cited references that it was made to avoid, may needto be revisited. Further, any disclaimer made in the instant applicationshould not be read into or against the parent application or otherrelated applications.

TECHNICAL FIELD

The present application relates to wireless communication, including totechniques for performing radio link monitoring using downlink controland data decoding performance characteristics.

DESCRIPTION OF THE RELATED ART

Wireless communication systems are rapidly growing in usage. Further,wireless communication technology has evolved from voice-onlycommunications to also include the transmission of data, such asInternet and multimedia content.

Mobile electronic devices may take the form of smart phones or tabletsthat a user typically carries. Wearable devices (also referred to asaccessory devices) are a newer form of mobile electronic device, oneexample being smart watches. Additionally, low-cost low-complexitywireless devices intended for stationary or nomadic deployment are alsoproliferating as part of the developing “Internet of Things”. Many suchdevices have relatively limited wireless communications capabilities andtypically have smaller batteries than larger portable devices, such assmart phones and tablets. In general, it would be desirable to recognizeand provide support for the relatively limited wireless communicationcapabilities of such devices. Therefore, improvements in the field aredesired.

SUMMARY

Embodiments are presented herein of, inter alia, systems, apparatuses,and methods for a wireless device to perform radio link monitoring usingdownlink control and data decoding performance characteristics.

In many instances, a wireless device may be able to monitor and evaluatea radio link based effectively primarily or exclusively based onreference signals provided by its serving base station. However, theremay be many instances in which such techniques may not provide the mostaccurate evaluation of the radio link. For instance, in some scenarios,a link-budget-limited wireless device may benefit from power boosting ofcontrol and/or data resource elements, while the reference signals maynot be power boosted. This power boosting may enable the wireless deviceto successfully receive and decode control and/or data signals moreeffectively than might be indicated by evaluating the radio link basedon (unboosted) reference signals.

Accordingly, techniques are described herein for supplementing radiolink monitoring techniques with the use of characteristics of decodingperformance for control and/or data signals, e.g., in addition to theuse of reference signals. According to the techniques described herein,a wireless device may be able to modify its radio link monitoringcriteria for when the wireless device is in-sync or out-of-sync based atleast in part on the decoding performance for control and/or datasignals, and/or may be able to reset or modify an out-of-sync counter,an out-of-sync timer, and/or an in-sync counter based on whetherdecoding performance for control and/or data signals is or is notsatisfactory during each of one or more evaluation periods.

Such techniques may enable a wireless device to successfully communicateusing a radio link that might otherwise be deemed unsustainable, e.g.,if the wireless device is able to recognize the availability of and makeuse of network-assist features for coverage constrained wireless device,and/or in any of various other (e.g., coverage constrained ornon-coverage constrained) possible scenarios.

The techniques described herein may be implemented in and/or used with anumber of different types of devices, including but not limited tocellular phones, tablet computers, accessory and/or wearable computingdevices, portable media players, cellular base stations and othercellular network infrastructure equipment, servers, and any of variousother computing devices.

This summary is intended to provide a brief overview of some of thesubject matter described in this document. Accordingly, it will beappreciated that the above-described features are merely examples andshould not be construed to narrow the scope or spirit of the subjectmatter described herein in any way. Other features, aspects, andadvantages of the subject matter described herein will become apparentfrom the following Detailed Description, Figures, and Claims.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the present subject matter can be obtainedwhen the following detailed description of the embodiments is consideredin conjunction with the following drawings.

FIG. 1 illustrates an example wireless communication system including anaccessory device, according to some embodiments;

FIG. 2 illustrates an example system where an accessory device canselectively either directly communicate with a cellular base station orutilize the cellular capabilities of an intermediate or proxy devicesuch as a smart phone, according to some embodiments;

FIG. 3 is a block diagram illustrating an example wireless device,according to some embodiments;

FIG. 4 is a block diagram illustrating an example base station,according to some embodiments;

FIG. 5 is a flowchart diagram illustrating an exemplary method forperforming radio link monitoring using downlink control and datadecoding performance characteristics, according to some embodiments; and

FIGS. 6-8 are timing diagrams illustrating exemplary possible radio linkmonitoring scenarios for a wireless device capable of performing radiolink monitoring based at least in part on characteristics of decodingperformance for control and/or data signals, according to someembodiments.

While the features described herein are susceptible to variousmodifications and alternative forms, specific embodiments thereof areshown by way of example in the drawings and are herein described indetail. It should be understood, however, that the drawings and detaileddescription thereto are not intended to be limiting to the particularform disclosed, but on the contrary, the intention is to cover allmodifications, equivalents and alternatives falling within the spiritand scope of the subject matter as defined by the appended claims.

The term “configured to” is used herein to connote structure byindicating that the units/circuits/components include structure (e.g.,circuitry) that performs the task or tasks during operation. As such,the unit/circuit/component can be said to be configured to perform thetask even when the specified unit/circuit/component is not currentlyoperational (e.g., is not on). The units/circuits/components used withthe “configured to” language include hardware—for example, circuits,memory storing program instructions executable to implement theoperation, etc. Reciting that a unit/circuit/component is “configuredto” perform one or more tasks is expressly intended not to invokeinterpretation under 35 U.S.C. § 112(f) for that unit/circuit/component.

DETAILED DESCRIPTION Terminology

The following are definitions of terms used in this disclosure:

Memory Medium—Any of various types of non-transitory memory devices orstorage devices. The term “memory medium” is intended to include aninstallation medium, e.g., a CD-ROM, floppy disks, or tape device; acomputer system memory or random access memory such as DRAM, DDR RAM,SRAM, EDO RAM, Rambus RAM, etc.; a non-volatile memory such as a Flash,magnetic media, e.g., a hard drive, or optical storage; registers, orother similar types of memory elements, etc. The memory medium mayinclude other types of non-transitory memory as well or combinationsthereof. In addition, the memory medium may be located in a firstcomputer system in which the programs are executed, or may be located ina second different computer system which connects to the first computersystem over a network, such as the Internet. In the latter instance, thesecond computer system may provide program instructions to the firstcomputer for execution. The term “memory medium” may include two or morememory mediums which may reside in different locations, e.g., indifferent computer systems that are connected over a network. The memorymedium may store program instructions (e.g., embodied as computerprograms) that may be executed by one or more processors.

Carrier Medium—a memory medium as described above, as well as a physicaltransmission medium, such as a bus, network, and/or other physicaltransmission medium that conveys signals such as electrical,electromagnetic, or digital signals.

Programmable Hardware Element—includes various hardware devicescomprising multiple programmable function blocks connected via aprogrammable interconnect. Examples include FPGAs (Field ProgrammableGate Arrays), PLDs (Programmable Logic Devices), FPOAs (FieldProgrammable Object Arrays), and CPLDs (Complex PLDs). The programmablefunction blocks may range from fine grained (combinatorial logic or lookup tables) to coarse grained (arithmetic logic units or processorcores). A programmable hardware element may also be referred to as“reconfigurable logic”.

Computer System—any of various types of computing or processing systems,including a personal computer system (PC), mainframe computer system,workstation, network appliance, Internet appliance, personal digitalassistant (PDA), television system, grid computing system, or otherdevice or combinations of devices. In general, the term “computersystem” can be broadly defined to encompass any device (or combinationof devices) having at least one processor that executes instructionsfrom a memory medium.

User Equipment (UE) (or “UE Device”)—any of various types of computersystems devices which are mobile or portable and which performs wirelesscommunications. Examples of UE devices include mobile telephones orsmart phones (e.g., iPhone™, Android™-based phones), portable gamingdevices (e.g., Nintendo DS™, PlayStation Portable™, Gameboy Advance™,iPhone™), laptops, wearable devices (e.g. smart watch, smart glasses),PDAs, portable Internet devices, music players, data storage devices, orother handheld devices, etc. In general, the term “UE” or “UE device”can be broadly defined to encompass any electronic, computing, and/ortelecommunications device (or combination of devices) which is easilytransported by a user and capable of wireless communication.

Wireless Device—any of various types of computer system devices whichperforms wireless communications. A wireless device can be portable (ormobile) or may be stationary or fixed at a certain location. A UE is anexample of a wireless device.

Communication Device—any of various types of computer systems or devicesthat perform communications, where the communications can be wired orwireless. A communication device can be portable (or mobile) or may bestationary or fixed at a certain location. A wireless device is anexample of a communication device. A UE is another example of acommunication device.

Base Station—The term “Base Station” (also called “eNB”) has the fullbreadth of its ordinary meaning, and at least includes a wirelesscommunication station installed at a fixed location and used tocommunicate as part of a wireless cellular communication system.

Link Budget Limited—includes the full breadth of its ordinary meaning,and at least includes a characteristic of a wireless device (a UE) whichexhibits limited communication capabilities, or limited power, relativeto a device that is not link budget limited, or relative to devices forwhich a radio access technology (RAT) standard has been developed. A UEthat is link budget limited may experience relatively limited receptionand/or transmission capabilities, which may be due to one or morefactors such as device design, device size, battery size, antenna sizeor design, transmit power, receive power, current transmission mediumconditions, and/or other factors. Such devices may be referred to hereinas “link budget limited” (or “link budget constrained”) devices. Adevice may be inherently link budget limited due to its size, batterypower, and/or transmit/receive power. For example, a smart watch that iscommunicating over LTE or LTE-A with a base station may be inherentlylink budget limited due to its reduced transmit/receive power and/orreduced antenna. Wearable devices, such as smart watches, are generallylink budget limited devices. Alternatively, a device may not beinherently link budget limited, e.g., may have sufficient size, batterypower, and/or transmit/receive power for normal communications over LTEor LTE-A, but may be temporarily link budget limited due to currentcommunication conditions, e.g., a smart phone being at the edge of acell, etc. It is noted that the term “link budget limited” includes orencompasses power limitations, and thus a power limited device may beconsidered a link budget limited device.

Processing Element (or Processor)—refers to various elements orcombinations of elements. Processing elements include, for example,circuits such as an ASIC (Application Specific Integrated Circuit),portions or circuits of individual processor cores, entire processorcores, individual processors, programmable hardware devices such as afield programmable gate array (FPGA), and/or larger portions of systemsthat include multiple processors.

Automatically—refers to an action or operation performed by a computersystem (e.g., software executed by the computer system) or device (e.g.,circuitry, programmable hardware elements, ASICs, etc.), without userinput directly specifying or performing the action or operation. Thusthe term “automatically” is in contrast to an operation being manuallyperformed or specified by the user, where the user provides input todirectly perform the operation. An automatic procedure may be initiatedby input provided by the user, but the subsequent actions that areperformed “automatically” are not specified by the user, i.e., are notperformed “manually”, where the user specifies each action to perform.For example, a user filling out an electronic form by selecting eachfield and providing input specifying information (e.g., by typinginformation, selecting check boxes, radio selections, etc.) is fillingout the form manually, even though the computer system must update theform in response to the user actions. The form may be automaticallyfilled out by the computer system where the computer system (e.g.,software executing on the computer system) analyzes the fields of theform and fills in the form without any user input specifying the answersto the fields. As indicated above, the user may invoke the automaticfilling of the form, but is not involved in the actual filling of theform (e.g., the user is not manually specifying answers to fields butrather they are being automatically completed). The presentspecification provides various examples of operations beingautomatically performed in response to actions the user has taken.

FIG. 1—Wireless Communication System

FIG. 1 illustrates an example of a wireless cellular communicationsystem. It is noted that FIG. 1 represents one possibility among many,and that features of the present disclosure may be implemented in any ofvarious systems, as desired. For example, embodiments described hereinmay be implemented in any type of wireless device.

As shown, the exemplary wireless communication system includes acellular base station 102, which communicates over a transmission mediumwith one or more wireless devices 106A, 106B, etc., as well as accessorydevice 107. Wireless devices 106A, 106B, and 107 may be user devices,which may be referred to herein as “user equipment” (UE) or UE devices.

The base station 102 may be a base transceiver station (BTS) or cellsite, and may include hardware that enables wireless communication withthe UE devices 106A, 106B, and 107. The base station 102 may also beequipped to communicate with a network 100 (e.g., a core network of acellular service provider, a telecommunication network such as a publicswitched telephone network (PSTN), and/or the Internet, among variouspossibilities). Thus, the base station 102 may facilitate communicationamong the UE devices 106 and 107 and/or between the UE devices 106/107and the network 100. In other implementations, base station 102 can beconfigured to provide communications over one or more other wirelesstechnologies, such as an access point supporting one or more WLANprotocols, such as 802.11a, b, g, n, ac, ad, and/or ax, or LTE in anunlicensed band (LAA).

The communication area (or coverage area) of the base station 102 may bereferred to as a “cell.” The base station 102 and the UEs 106/107 may beconfigured to communicate over the transmission medium using any ofvarious radio access technologies (RATs) or wireless communicationtechnologies, such as GSM, UMTS (WCDMA, TDS-CDMA), LTE, LTE-Advanced(LTE-A), NR, HSPA, 3GPP2 CDMA2000 (e.g., 1×RTT, 1×EV-DO, HRPD, eHRPD),Wi-Fi, WiMAX etc.

Base station 102 and other similar base stations (not shown) operatingaccording to one or more cellular communication technologies may thus beprovided as a network of cells, which may provide continuous or nearlycontinuous overlapping service to UE devices 106A-N and 107 and similardevices over a geographic area via one or more cellular communicationtechnologies.

Note that at least in some instances a UE device 106/107 may be capableof communicating using any of a plurality of wireless communicationtechnologies. For example, a UE device 106/107 might be configured tocommunicate using one or more of GSM, UMTS, CDMA2000, WiMAX, LTE, LTE-A,NR, WLAN, Bluetooth, one or more global navigational satellite systems(GNSS, e.g., GPS or GLONASS), one and/or more mobile televisionbroadcasting standards (e.g., ATSC-M/H), etc. Other combinations ofwireless communication technologies (including more than two wirelesscommunication technologies) are also possible. Likewise, in someinstances a UE device 106/107 may be configured to communicate usingonly a single wireless communication technology.

The UEs 106A and 106B are typically handheld devices such as smartphones or tablets, but may be any of various types of device withcellular communications capability. The UE 106B may be configured tocommunicate with the UE device 107, which may be referred to as anaccessory device 107. The accessory device 107 may be any of varioustypes of wireless devices, typically a wearable device that has asmaller form factor, and may have limited battery, output power and/orcommunications abilities relative to UEs 106. As one common example, theUE 106B may be a smart phone carried by a user, and the accessory device107 may be a smart watch worn by that same user. The UE 106B and theaccessory device 107 may communicate using any of various short rangecommunication protocols, such as Bluetooth or Wi-Fi.

The accessory device 107 includes cellular communication capability andhence is able to directly communicate with cellular base station 102.However, since the accessory device 107 is possibly one or more ofcommunication, output power and/or battery limited, the accessory device107 may in some instances selectively utilize the UE 106B as a proxy forcommunication purposes with the base station 102 and hence to thenetwork 100. In other words, the accessory device 107 may selectivelyuse the cellular communication capabilities of the UE 106B to conductits cellular communications. The limitation on communication abilitiesof the accessory device 107 can be permanent, e.g., due to limitationsin output power or the radio access technologies (RATs) supported, ortemporary, e.g., due to conditions such as current battery status,inability to access a network, or poor reception.

FIG. 2 illustrates an example accessory device 107 in communication withbase station 102. The accessory device 107 may be a wearable device suchas a smart watch. The accessory device 107 may comprise cellularcommunication capability and be capable of directly communicating withthe base station 102 as shown. When the accessory device 107 isconfigured to directly communicate with the base station, the accessorydevice may be said to be in “autonomous mode.”

The accessory device 107 may also be capable of communicating withanother device (e.g., UE 106), referred to as a proxy device orintermediate device, using a short range communications protocol; forexample, the accessory device 107 may according to some embodiments be“paired” with the UE 106. Under some circumstances, the accessory device107 may use the cellular functionality of this proxy device forcommunicating cellular voice/data with the base station 102. In otherwords, the accessory device 107 may provide voice/data packets intendedfor the base station 102 over the short range link to the UE 106, andthe UE 106 may use its cellular functionality to transmit (or relay)this voice/data to the base station on behalf of the accessory device107. Similarly, the voice/data packets transmitted by the base stationand intended for the accessory device 107 may be received by thecellular functionality of the UE 106 and then may be relayed over theshort range link to the accessory device. As noted above, the UE 106 maybe a mobile phone, a tablet, or any other type of hand-held device, amedia player, a computer, a laptop or virtually any type of wirelessdevice. When the accessory device 107 is configured to indirectlycommunicate with the base station using the cellular functionality of anintermediate or proxy device, the accessory device may be said to be in“relay mode.”

The UE 106 and/or 107 may include a device or integrated circuit forfacilitating cellular communication, referred to as a cellular modem.The cellular modem may include one or more processors (processorelements) and various hardware components as described herein. The UE106 and/or 107 may perform any of the method embodiments describedherein by executing instructions on one or more programmable processors.Alternatively, or in addition, the one or more processors may be one ormore programmable hardware elements such as an FPGA (field-programmablegate array), or other circuitry, that is configured to perform any ofthe method embodiments described herein, or any portion of any of themethod embodiments described herein. The cellular modem described hereinmay be used in a UE device as defined herein, a wireless device asdefined herein, or a communication device as defined herein. Thecellular modem described herein may also be used in a base station orother similar network side device.

The UE 106 and/or 107 may include one or more antennas for communicatingusing two or more wireless communication protocols or radio accesstechnologies. In some embodiments, the UE device 106/107 might beconfigured to communicate using a single shared radio. The shared radiomay couple to a single antenna, or may couple to multiple antennas(e.g., for MIMO) for performing wireless communications. Alternatively,the UE device 106/107 may include two or more radios. Otherconfigurations are also possible.

The accessory device 107 may be any of various types of devices that, insome embodiments, has a smaller form factor relative to a conventionalsmart phone, and may have one or more of limited communicationcapabilities, limited output power, or limited battery life relative toa conventional smart phone. As noted above, in some embodiments, theaccessory device 107 is a smart watch or other type of wearable device.As another example, the accessory device 107 may be a tablet device,such as an iPad, with Wi-Fi capabilities (and possibly limited or nocellular communication capabilities), which is not currently near aWi-Fi hotspot and hence is not currently able to communicate over Wi-Fiwith the Internet. Thus, as defined above, the term “accessory device”refers to any of various types of devices that in some instances havelimited or reduced communication capabilities and hence may selectivelyand opportunistically utilize the UE 106 as a proxy for communicationpurposes for one or more applications and/or RATs. When the UE 106 iscapable of being used by the accessory device 107 as a proxy, the UE 106may be referred to as a companion device to the accessory device 107.

FIG. 3—Example Block Diagram of a UE Device

FIG. 3 illustrates one possible block diagram of an UE device, such asUE device 106 or 107. As shown, the UE device 106/107 may include asystem on chip (SOC) 300, which may include portions for variouspurposes. For example, as shown, the SOC 300 may include processor(s)302 which may execute program instructions for the UE device 106/107,and display circuitry 304 which may perform graphics processing andprovide display signals to the display 360. The SOC 300 may also includemotion sensing circuitry 370 which may detect motion of the UE 106, forexample using a gyroscope, accelerometer, and/or any of various othermotion sensing components. The processor(s) 302 may also be coupled tomemory management unit (MMU) 340, which may be configured to receiveaddresses from the processor(s) 302 and translate those addresses tolocations in memory (e.g., memory 306, read only memory (ROM) 350, flashmemory 310). The MMU 340 may be configured to perform memory protectionand page table translation or set up. In some embodiments, the MMU 340may be included as a portion of the processor(s) 302.

As shown, the SOC 300 may be coupled to various other circuits of the UE106/107. For example, the UE 106/107 may include various types of memory(e.g., including NAND flash 310), a connector interface 320 (e.g., forcoupling to a computer system, dock, charging station, etc.), thedisplay 360, and wireless communication circuitry 330 (e.g., for LTE,LTE-A, NR, CDMA2000, Bluetooth, Wi-Fi, NFC, GPS, etc.).

The UE device 106/107 may include at least one antenna, and in someembodiments multiple antennas 335 a and 335 b, for performing wirelesscommunication with base stations and/or other devices. For example, theUE device 106/107 may use antennas 335 a and 335 b to perform thewireless communication. As noted above, the UE device 106/107 may insome embodiments be configured to communicate wirelessly using aplurality of wireless communication standards or radio accesstechnologies (RATs).

The wireless communication circuitry 330 may include Wi-Fi Logic 332, aCellular Modem 334, and Bluetooth Logic 336. The Wi-Fi Logic 332 is forenabling the UE device 106/107 to perform Wi-Fi communications on an802.11 network. The Bluetooth Logic 336 is for enabling the UE device106/107 to perform Bluetooth communications. The cellular modem 334 maybe a lower power cellular modem capable of performing cellularcommunication according to one or more cellular communicationtechnologies.

As described herein, UE 106/107 may include hardware and softwarecomponents for implementing embodiments of this disclosure. For example,one or more components of the wireless communication circuitry 330(e.g., cellular modem 334) of the UE device 106/107 may be configured toimplement part or all of the methods described herein, e.g., by aprocessor executing program instructions stored on a memory medium(e.g., a non-transitory computer-readable memory medium), a processorconfigured as an FPGA (Field Programmable Gate Array), and/or usingdedicated hardware components, which may include an ASIC (ApplicationSpecific Integrated Circuit).

FIG. 4—Block Diagram of a Base Station

FIG. 4 illustrates an example block diagram of a base station 102,according to some embodiments. It is noted that the base station of FIG.4 is merely one example of a possible base station. As shown, the basestation 102 may include processor(s) 404 which may execute programinstructions for the base station 102. The processor(s) 404 may also becoupled to memory management unit (MMU) 440, which may be configured toreceive addresses from the processor(s) 404 and translate thoseaddresses to locations in memory (e.g., memory 460 and read only memory(ROM) 450) or to other circuits or devices.

The base station 102 may include at least one network port 470. Thenetwork port 470 may be configured to couple to a telephone network andprovide a plurality of devices, such as UE devices 106/107, access tothe telephone network as described above in FIGS. 1 and 2.

The network port 470 (or an additional network port) may also oralternatively be configured to couple to a cellular network, e.g., acore network of a cellular service provider. The core network mayprovide mobility related services and/or other services to a pluralityof devices, such as UE devices 106/107. In some cases, the network port470 may couple to a telephone network via the core network, and/or thecore network may provide a telephone network (e.g., among other UEdevices serviced by the cellular service provider).

The base station 102 may include at least one antenna 434, and possiblymultiple antennas. The antenna(s) 434 may be configured to operate as awireless transceiver and may be further configured to communicate withUE devices 106/107 via radio 430. The antenna(s) 434 communicates withthe radio 430 via communication chain 432. Communication chain 432 maybe a receive chain, a transmit chain or both. The radio 430 may beconfigured to communicate via various wireless communication standards,including, but not limited to, LTE, LTE-A, NR, GSM, UMTS, CDMA2000,Wi-Fi, etc.

The base station 102 may be configured to communicate wirelessly usingmultiple wireless communication standards. In some instances, the basestation 102 may include multiple radios, which may enable the basestation 102 to communicate according to multiple wireless communicationtechnologies. For example, as one possibility, the base station 102 mayinclude an LTE radio for performing communication according to LTE aswell as a Wi-Fi radio for performing communication according to Wi-Fi.In such a case, the base station 102 may be capable of operating as bothan LTE base station and a Wi-Fi access point. As another possibility,the base station 102 may include a multi-mode radio which is capable ofperforming communications according to any of multiple wirelesscommunication technologies (e.g., LTE and Wi-Fi, LTE and UMTS, LTE andCDMA2000, UMTS and GSM, etc.).

As described further subsequently herein, the BS 102 may includehardware and software components for implementing or supportingimplementation of features described herein. The processor 404 of thebase station 102 may be configured to implement or supportimplementation of part or all of the methods described herein, e.g., byexecuting program instructions stored on a memory medium (e.g., anon-transitory computer-readable memory medium). Alternatively, theprocessor 404 may be configured as a programmable hardware element, suchas an FPGA (Field Programmable Gate Array), or as an ASIC (ApplicationSpecific Integrated Circuit), or a combination thereof. Alternatively(or in addition) the processor 404 of the BS 102, in conjunction withone or more of the other components 430, 432, 434, 440, 450, 460, 470may be configured to implement or support implementation of part or allof the features described herein.

FIG. 5—Flowchart

FIG. 5 is a flowchart diagram illustrating a method for a wirelessdevice to perform radio link monitoring using downlink control and datadecoding performance characteristics, according to some embodiments. Invarious embodiments, some of the elements of the methods shown may beperformed concurrently, in a different order than shown, may besubstituted for by other method elements, or may be omitted. Additionalmethod elements may also be performed as desired.

Aspects of the method of FIG. 5 may be implemented by a wireless device,such as a UE 106 or 107 illustrated in and described with respect toFIGS. 1-3, or more generally in conjunction with any of the computersystems or devices shown in the above Figures, among other devices, asdesired. As shown, the method may operate as follows.

In 502, the wireless device may establish a radio link with a cellularbase station. The radio link may operate according to a radio accesstechnology, such as LTE, LTE-A, NR, WCDMA, etc. According to someembodiments, establishing the radio link may include any or all ofacquiring system information for a cell deployed by a public land mobilenetwork (PLMN), performing an attach procedure to attach to the PLMN byway of the cell (e.g., such that the cell acts as a serving cell for thewireless device), and establishing a radio resource control (RRC)connection with the serving cell. The serving cell may be provided by acellular base station operated by the PLMN.

The wireless device and the cellular base station may perform controland data communication via the radio link. For example, in LTE, a basestation may provide control signals via a physical downlink controlchannel (PDCCH) and may provide data signals via a physical downlinkshared channel (PDSCH), according to some embodiments. In addition, thebase station may provide reference signals (e.g., to assist with channelestimation, radio link monitoring, etc.), such as cell-specificreference signals (CRS), to the wireless device (and possibly to otherwireless devices in communication with the base station).

In 504, the wireless device may perform radio link monitoring of theradio link using characteristics of decoding performance for controland/or data signals. The characteristics of decoding performance forcontrol and/or data signals may be used to supplement the use of thereference signals provided by the base station to perform radio linkmonitoring, according to some embodiments.

For example, in some embodiments, performing radio link monitoring (RLM)may include determining one or more signal quality metric values (e.g.,a signal to noise ratio (SNR)) of reference signals (e.g., CRS) providedby the base station via the radio link over the course of a radio linkmonitoring window, for each of multiple such radio link monitoringwindows. The SNR (and/or other signal quality metric value) may befiltered (e.g., averaged over time) in any of various possible ways, ifdesired. For example, the SNR may be filtered over a RLM window (e.g.,200 ms for non-DRX while out-of-sync or 100 ms for non-DRX whilein-sync, as one possibility) configured by the base station and/ordetermined from standard specification documents.

Once the SNR of the CRS is determined, it may be compared to one or moreSNR threshold values, and/or possibly mapped to a block error rate(BLER) of decoding a hypothetical control signal from the base stationand then compared to one or more BLER thresholds, to determine whetherthe wireless device is in-sync (e.g., if the SNR/hypothetical BLER isbetter than an in-sync threshold, which may also be referred to as “Qin”herein) or out-of-sync (e.g., if the SNR/hypothetical BLER is worse thanan out-of-sync threshold, which may also be referred to as “Qout”herein). According to some embodiments, Qout may be represented by afiltered CRS SNR threshold that maps to achieving 10% hypothetical PDCCHBLER, while Qin may be represented by a filtered CRS SNR threshold thatmaps to achieving 2% hypothetical PDCCH BLER. Other Qout/Qinrepresentations are also possible.

In-sync and out-of-sync counters may be maintained, and may beincremented if it is determined that the wireless device is in-sync orout-of-sync for a particular RLM window. According to some embodiments,if the out-of-sync counter reaches a certain threshold (e.g., if thewireless device has been out-of-sync a certain number of consecutivetimes), it may be determined that radio link failure has occurred. Asanother possibility, one or more timers (e.g., an out-of-sync timer) mayalso or alternatively be utilized as part of determining when radio linkfailure has occurred.

In some embodiments, using the characteristics of decoding performancefor one or more of the control signals and the data signals as part ofperforming radio link monitoring may include determining a modificationto each of one or more SNR and/or BLER threshold values (e.g., thein-sync threshold and/or the out-of-sync threshold) based on thedecoding performance characteristics.

For example, in some instances the base station may power boost certaincontrol channel (e.g., PDCCH, PHICH) and data channel (e.g., PDSCH)transmissions intended for coverage-constrained (e.g., link budgetlimited) wireless devices. However, in some instances, power boostingmay not be applied to the resource elements carrying reference signals(e.g., CRS tones), e.g., to avoid causing potentially harmfulinterference to neighboring cells (or for any of a variety of otherpossible reasons).

In such a case, the SNR perceived on the CRS tones may not reflect theactual PDCCH/PDSCH decoding performance with PDCCH/PDSCH power boosting,so performing RLM without accounting for how such power boosting of thePDCCH/PDSCH may affect their decoding may not provide the most helpfulindication of the state of the radio link. Accordingly, it may bebeneficial to modify (e.g., bias) the SNR and/or BLER thresholds usedwith respect to the CRS SNR/hypothetical BLER to account for any controland/or data signal power boosting. For example, this may allow suchnetwork-assisted coverage-constrained UEs to benefit from power boostingin terms of extended coverage where an RLM algorithm that utilizes CRSSNR without taking into consideration network-assisted power boostingmight deem the link unsustainable.

According to some embodiments, the base station may utilize a staticpower boosting factor to boost some or all control signals and datasignals for the wireless device (e.g., indefinitely or for a specifiedperiod of time), such that the wireless device may be able to directlydetermine that power boosting is occuring for control and/or datasignals intended for it. For example, the base station may signal anindication of the value of the power boosting factor (and possibly alength of time for which the power boosting will be active) to thewireless device using control signaling. As another possibility, thebase station may be pre-configured to implicitly implement static powerboosting of certain resource elements (e.g., those carrying PDCCHsignaling intended for the wireless device, those carrying PDSCHsignaling intended for the wireless device, etc.) under certainconditions and/or based on certain triggers, e.g., which may bepre-agreed between the wireless device maker/vendor and theoperator/maker/vendor of the base station, such that the wireless devicecan determine that power boosting by a particular power boosting factorfor certain control and/or data signals will occur for a particularperiod of time based on a triggering event or condition occurring. Othertechniques for utilizing static power boosting (including techniques fora wireless device to directly determine when such static power boostingis occurring) are also possible.

Alternatively or in addition, according to some embodiments, the basestation may not always be able to boost the control and data resourceelements intended for the wireless device, and/or may not always be ableto apply maximum power boosting to such resource elements, for exampledue to network loading and/or other considerations, and so maydynamically determine which resource elements to power boost and by howmuch, such that the wireless device is unable to directly determine howmuch power boosting is being applied by the base station at least someof the time.

In such instances, the wireless device may be able to infer the (e.g.,average or approximate) power boosting factor used by the base stationto boost transmit power of the control and/or data signals, e.g., basedon measured characteristics of received control and/or data signals, andmodify its RLM technique accordingly. For example, an amount of biasapplied to the in-sync threshold and/or out-of-sync threshold for a RLMevaluation period may be determined based on measurement of the energymetric for successfully received control signals (e.g., PDCCH controlchannel elements (CCEs)), possibly in combination with one or more othermetrics and/or configuration settings, during that RLM evaluationperiod. As one possibility, a pre-characterized or dynamic mapping ofthe energy metric to threshold modification factor(s) based on any orall of PDCCH aggregation level, PDCCH payload size, reference signalreceived power (RSRP)/path loss, power boosting level, and/or PDCCH CCEloading may be used.

In some embodiments, the actual received and successfully decodedcontrol (e.g., PDCCH) subframes may be factored into the choice ofin-sync threshold and/or out-of-sync threshold for an evaluation period.In other words, Qout/Qin may be adapted per evaluation period, based onactual received PDCCH subframes. Qout/Qin may also be adjusted (e.g.,up/down, via positive/negative bias) based on lack of reception ofPDCCH. Since channel estimation may also be dependent on CRS receivedpower/SNR, and channel estimation affects both the detection/decoding ofPDCCH and PDSCH subframes, adaptation of Qout/Qin may also take intoconsideration PDSCH (data channel) BLER, at least in some instances.

Note that while the wireless device may be able to directly determinewhen it is able to successfully decode control and data signals, it maynot always be able to directly determine when it has missed control anddata signals. However, at least in some instances, the wireless devicemay be able to infer some or all instances of missed control and/or datasignals.

For example, the wireless device may be able to use symbol energymetrics and Tail Biting properties of the convolutional codes used onthe PDCCH to detect a missed transmission, in some embodiments.Convolutional decoding via block trellis decoding may suffer unequalerror protection. The end bits of a block decoder may suffer from lowerreliability if no tail bits are present. Adding zero tail bits (ZTCC)and coding these bits decreases the code rate significantly for shortertransport block sizes. Tail biting convolution codes may thus help inincreasing reliability while preserving the code rate. The encoder inTBCC starts and ends with first few information bits to indicate the endof a transmitted sequence. At the receiver, it may accordingly bepossible to consider all the received sequences which start and end withthe same state. Since LTE constraint length is 7 (at least according tosome embodiments), it results in 6 additional bits and thus 64 possiblestates to consider. To reduce decoding complexity only a subset of thesestates may be considered. In order to realize the full gain of MLD in TBcodes, a UE may be able to use techniques such as a modified Viterbialgorithm, repetitive decoding, typically used in decoding generalizedtail-biting codes to realize full code rate gains. This could give theUE an additional gain of approximately 1 dB in blind decodingperformance. Even if further decoding of PDCCH bits fails, the UE may beable to check the tail with the initial bits to make a determination onwhether a PDCCH transmission is attempted.

As another example, in cases where semi-persistent-scheduling (SPS)grants are scheduled (e.g., such a grant may typically be scheduledperiodically for a fixed duration), the wireless device may be able todetermine if it has missed detection of PDSCH signals based on theperiodicity of such a grant.

As a further possibility, when PDCCH boosting is enabled, based on thephysical control format indicator channel (PCFICH) signaled by thenetwork, the wireless device may be able to perform traffic to pilotratio (TPR) estimation over the resource blocks in UE specific searchspace where PDCCH symbols are expected, e.g., to differentiate powerboosting vs. non-boosting cases.

The wireless device may also be able to consider the redundancy version(RV) sequence over a period of time (e.g., 4 ms per 1 hybrid automaticrepeat request (HARD), as one possibility) typically used (and possiblyfixed) by the network on the PDSCH and use this to count the number ofPDCCH decode failures.

As a still further possibility, the wireless device may be able to inferthat it has missed downlink control information based on downlinkassignment index (DAI) information (e.g., when time division duplexing(TDD) LTE is used). The DAI may be signaled in downlink controlinformation (DCI) in the PDCCH payload, and may be used to help thewireless device report accurate acknowledgement (e.g., ACK/NACK)information for received downlink grants to the base station. In a givensubframe in which the wireless device has successfully decoded thePDCCH, the DAI field may reflect the number of downlink grants sent bythe network since the last uplink bundled ACK/NACK subframe providedfrom the wireless device to the network. Thus, if this number is greaterthan the actual number of downlink grants received at the wirelessdevice, the wireless device may be able to infer that it has missedPDCCH subframes in the period of time since the most recent uplinkbundled ACK/NACK subframe, e.g., amounting to the difference between thenetwork-signaled number of downlink grants and the number of downlinkgrants actually received by the wireless device.

Based on such techniques for determining when control and/or datasignals intended for the wireless device were not detected, and based ondetermining how many control and/or data signals intended for thewireless device were successfully received and decoded, the wirelessdevice may be able to estimate a decoding success rate for controlsignals and/or for data signals, e.g., over the RLM window.

Note that in addition to or as an alternative to biasing the in-syncand/or out-of sync threshold(s), the RLM procedure may be modified tomanipulate the out-of-sync/in-sync count (e.g., N310/N311 values,according to LTE) and/or timers, e.g., to similarly increase the degreeto which radio link monitoring is based on actual decoding of controland/or data signals during the monitoring interval. For example, as onepossibility, if characteristics of actual decoding of control and/ordata signals are indicative of a BLER better than that represented bythe default Qout value, the out-of-sync count may be de-incremented,reset, or at least not incremented, even if the CRS SNR taken alonewould result in an out-of-sync condition. Other such out-of-sync/in-synccount/timer modifications based on characteristics of control and/ordata signal decoding are also possible.

Note that, at least according to some embodiments, the use of any or allof the characteristics of decoding performance for the control and/ordata signals described herein when performing radio link monitoring maybe applied selectively, if desired. For example, the wireless device mayperform radio link monitoring based on the reference signals provided bythe cellular base station without using the characteristics of decodingperformance for the control and/or data signals at some times, and mayperform radio link monitoring based on the reference signals provided bythe cellular base station and also using the characteristics of decodingperformance for the control and/or data signals at other times. Thewireless device may determine whether to use the characteristics ofdecoding performance for the control and/or data signals in any of avariety of possible ways. As one possibility, the characteristics ofdecoding performance for the control and/or data signals may be usedonce a certain number of out-of-sync instances have occurred (e.g., oncean out-of-sync counter reaches a threshold for implementing the use ofcharacteristics of decoding performance for the control and/or datasignals for radio link monitoring), and, once implemented, may ceasebeing used once a certain number of in-sync instances have occurred(e.g., once an in-sync counter reaches a threshold for ceasing the useof characteristics of decoding performance for the control and/or datasignals for radio link monitoring).

According to some embodiments, a modulation and coding scheme (MCS) usedfor transmission of data signals from the base station to the wirelessdevice may be considered as part of the radio link monitoring algorithmand/or for determining when the radio link is and is not sustainable.For example, if the downlink performance metrics for control and dataare poor (e.g., BLER is above a BLER threshold for RLF, such as 20%BLER), but the current MCS is not the lowest possible (e.g., mostrobust) MCS, it may be possible that a reduction in MCS may improve theBLER and the radio link may be sustainable without triggering RLF. Insuch a case, the wireless device might enable a timer (e.g., ahysteresis timer) to provide the network with time to converge on theouter loop and schedule a lower MCS. Such a reduction in MCS, if itoccurs, may trigger re-evaluation of the radio link, according to someembodiments, as BLER experienced on the radio link may decrease with thelower MCS; however, if the timer expires without a change of MCS, thewireless device may trigger RLF, e.g., rather than continuing to waitindefinitely for an MCS reduction that may not be forthcoming. The timerlength may be determined in any of various possible manners, as desired,such as using laboratory measurements to optimize the timer length for adesired outcome according to one or more metrics, possibly depending onwhich network the wireless device is attached to.

According to some embodiments, if the scheduled MCS is greater than orequal to the lowest possible MCS and the downlink performance metricsfor control and data are acceptable (e.g., BLER is below a BLERthreshold for RLF), it may be determined that the wireless device cansustain the radio link without triggering RLF. If, on the other hand,the scheduled MCS is already at the lowest possible MCS and the downlinkperformance metrics for control and data are poor (e.g., BLER is above aBLER threshold for RLF), it may be determined that network powerboosting (if any) provided by the base station is not helpingsufficiently and the wireless device may trigger RLF.

Note that any or all of the techniques for performing radio linkmonitoring using characteristics of decoding performance for controlsignals and/or data signals may be used in combination, if desired. Forexample, according to some embodiments, some or all aspects of thetechniques described herein may be used as part of an outer loop typealgorithm at the wireless device for utilizing decoding performancecharacteristics of control and data signals in combination withreference signals provided by the base station to provide a moreholistic view of the status of the radio link than by simply relying onthe reference signals alone.

Note further that while certain of the techniques described herein maybe useful primarily for coverage-constrained/link-budget-limited devicesthat receive network assistance in the form of control and/or datasignal power boosting, at least some of the techniques described hereinmay be useful more broadly for non link budget limited devices as well.For example, estimating a success rate of control and/or data signalreception and decoding and applying such an indication of actualdecoding performance as a supplement or alternative to reference signalbased hypothetical decoding performance, and considering a modulationand coding scheme for data signals when determining whether to triggerRLF, among other possible techniques, may improve radio link monitoringfor both link budget limited and non link budget limited wirelessdevices, according to some embodiments.

FIGS. 6-8—Example Timing Diagrams

FIGS. 6-8 are timing diagrams illustrating a number of possible radiolink monitoring scenarios that may occur for a wireless device capableof performing radio link monitoring based at least in part oncharacteristics of decoding performance for control and/or data signals,such as a wireless device configured to implement a method according toFIG. 5, according to some embodiments. Note that FIGS. 6-8 and thedescription thereof are provided by way of example, and are not intendedto be limiting to the disclosure as a whole. Numerous alternatives toand variations of the details provided herein below are possible andshould be considered within the scope of the present disclosure.

In the scenario of FIG. 6, a wireless device may initially perform radiolink monitoring based on reference signals provided by its serving basestation without utilizing downlink control and/or data decodingperformance characteristics. Using this radio link monitoring technique,the wireless device may determine that it is out-of-sync during athreshold number of out-of-sync instances (e.g., “N310”, which may bespecified by standard specification documents, selected by a networkinfrastructure maker/vendor/operator, and/or otherwise determined)configured to trigger initiation of an out-of-sync or radio link failuretimer (e.g., having a length “T310”, which may be specified by standardspecification documents, selected by a network infrastructuremaker/vendor/operator, and/or otherwise determined). The thresholdnumber of out-of-sync instances occurring may also trigger the wirelessdevice to begin utilizing downlink control and/or data decodingperformance characteristics when performing radio link monitoring for asubsequent evaluation window (which may be shorter than the length ofthe out-of-sync/radio link failure timer).

In this scenario, if the control and/or data decoding performance issatisfactory (e.g., meets one or more specified conditions) over anevaluation window, the out-of-sync/radio link failure timer may be resetand restarted, such as illustrated in the evaluation window 610. If,however, the control and/or data decoding performance is notsatisfactory (e.g., does not meet the one or more specified conditions)over an evaluation window, the out-of-sync/radio link failure timer maynot be modified (e.g., may keep running), such as illustrated in theevaluation window 620. This may eventually result in radio link failureoccurring if the out-of-sync/radio link failure timer expires, as shownin FIG. 6.

In the scenario of FIG. 7, the wireless device may similarly initiallyperform radio link monitoring based on reference signals provided by itsserving base station without utilizing downlink control and/or datadecoding performance characteristics. Using this radio link monitoringtechnique, the wireless device may also determine that it is out-of-syncduring N310 out-of-sync instances, triggering initiation of the T310timer. As in FIG. 6, the threshold number of out-of-sync instancesoccurring may also trigger the wireless device to begin utilizingdownlink control and/or data decoding performance characteristics whenperforming radio link monitoring for a subsequent evaluation window.

In this scenario, if the control and/or data decoding performance issatisfactory (e.g., meets one or more specified conditions) over anevaluation window, the out-of-sync/radio link failure timer may be resetand restarted, such as illustrated in the evaluation window 710. If theradio link monitoring subsequently determines that the radio link isin-sync during a threshold number of in-sync instances (e.g., “N311”,which may be specified by standard specification documents, selected bya network infrastructure maker/vendor/operator, and/or otherwisedetermined), the T310 timer may be stopped, and the wireless device maycease utilizing downlink control and/or data decoding performancecharacteristics for radio link monitoring (e.g., until the next time thenumber of out-of-sync instances reaches N310 and T310 starts again).Note that this may occur in the middle of an evaluation window, such asin the illustrated evaluation window 720.

In the scenario of FIG. 8, an alternate (or additional) approach may betaken to determining when to trigger use of downlink control and/or datadecoding performance characteristics for radio link monitoring. In thiscase, the downlink control and/or data decoding performancecharacteristics may be used for radio link monitoring once the firstout-of-sync instance occurs (or more generally upon the nth out-of-syncinstance, where n<N310; n=1 in the scenario of FIG. 8).

An evaluation window for using the downlink control and/or data decodingperformance characteristics for radio link monitoring may be denoted ast (e.g., in milliseconds). The evaluation window length t may vary indifferent circumstances, e.g., depending on whether the wireless deviceis currently in connected discontinuous reception (CDRX) or non-CDRXmode. At least according to some embodiments, the evaluation windowlength t may be selected such that it ends before the N310 count ofout-of-sync instances can be reached.

According to the scenario of FIG. 8, if the control and/or data decodingperformance is satisfactory over the evaluation window, the out-of-synccount may be reset (e.g., to 0) or reduced, such as illustrated in theevaluation windows 810, 820. If the control and/or data decodingperformance is not satisfactory over the evaluation window, theout-of-sync count may not be reset, and if it reaches the N310 value,the timer T310 may be started. If desired, the techniques described withrespect to FIGS. 6-7 may additionally be used to potentially reset theT310 timer once it has begun in this scenario.

Note that in the scenario of FIG. 8, it is also possible that the T310timer may not be started, e.g., due to the out-of-sync count notreaching N310, and due to radio conditions improving such that N311consecutive in-sync instances occur. In this case, the wireless devicemay cease utilizing downlink control and/or data decoding performancecharacteristics for radio link monitoring (e.g., until the next time thenumber of out-of-sync instances reaches n), possibly even if this occursin the middle of an evaluation window, such as in the illustratedevaluation window 830.

In the following further exemplary embodiments are provided.

One set of embodiments may include an apparatus, comprising: aprocessing element configured to cause a wireless device to: establish aradio link with a cellular base station according to a radio accesstechnology, wherein the base station provides reference signals, controlsignals, and data signals to the wireless device via the radio link;perform radio link monitoring of the radio link based at least in parton the reference signals; and determine whether to perform radio linkmonitoring of the radio link further based at least in part oncharacteristics of decoding performance for one or more of the controlsignals and the data signals, wherein performing radio link monitoringof the radio link is further based at least in part on thecharacteristics of decoding performance for one or more of the controlsignals and the data signals when it is determined to perform radio linkmonitoring of the radio link further based at least in part oncharacteristics of decoding performance for one or more of the controlsignals and the data signals.

According to some embodiments, performing radio link monitoring of theradio link comprises determining whether the radio link is in-sync orout-of-sync and determining whether radio link failure has occurred.

According to some embodiments, determining whether to perform radio linkmonitoring of the radio link further based at least in part oncharacteristics of decoding performance for one or more of the controlsignals and the data signals is based at least in part on whether anumber of out-of-sync instances reaches an out-of-sync threshold.

According to some embodiments, performing radio link monitoring of theradio link comprises, when it is determined not to perform radio linkmonitoring of the radio link further based at least in part oncharacteristics of decoding performance for one or more of the controlsignals and the data signals: determining a signal to noise ratio (SNR)of the reference signals during a monitoring window; comparing the SNRof the reference signals during the monitoring window to one or more SNRthreshold values to determine whether the radio link is in-sync orout-of-sync during the monitoring window; and determining whether radiolink failure has occurred based at least in part on whether the radiolink is in-sync or out-of-sync during the monitoring window, whereinperforming radio link monitoring of the radio link comprises, when it isdetermined to perform radio link monitoring of the radio link furtherbased at least in part on characteristics of decoding performance forone or more of the control signals and the data signals: determining asignal to noise ratio (SNR) of the reference signals during a monitoringwindow; determining a modification to one or more SNR threshold valuesbased on the characteristics of decoding performance for one or more ofthe control signals and the data signals during the monitoring window;comparing the SNR of the reference signals during the monitoring windowto the one or more modified SNR threshold values to determine whetherthe radio link is in-sync or out-of-sync during the monitoring window;and determining whether radio link failure has occurred based at leastin part on whether the radio link is in-sync or out-of-sync during themonitoring window.

According to some embodiments, wherein the characteristics of decodingperformance for one or more of the control signals and the data signalscomprise at least a power boosting factor used by the base station toboost transmit power of one or more of the control signals or the datasignals relative to the reference signals.

According to some embodiments, the processing element is furtherconfigured to cause the wireless device to, when performing radio linkmonitoring of the radio link based at least in part on the referencesignals and further based at least in part on characteristics ofdecoding performance for one or more of the control signals and the datasignals: reset one or more of an out-of-sync counter or an out-of-synctimer when decoding performance for one or more of the control signalsand the data signals during a monitoring window meets one or moreresetting criteria.

Another set of embodiments may include a method for a wireless device,comprising: establishing a radio link with a cellular base stationaccording to a radio access technology, wherein the base stationprovides reference signals, control signals, and data signals to thewireless device via the radio link; and performing radio link monitoringof the radio link using characteristics of decoding performance for oneor more of the control signals and the data signals, wherein performingradio link monitoring of the radio link comprises determining whetherthe radio link is in-sync or out-of-sync and determining whether radiolink failure has occurred.

According to some embodiments, radio link monitoring of the radio linkis further based at least in part on the reference signals.

According to some embodiments, performing radio link monitoring of theradio link comprises: determining a signal to noise ratio (SNR) ofcell-specific reference signals (CRS) provided by the base station viathe radio link; determining a modification to each of one or more SNRthreshold values based on the characteristics of decoding performancefor one or more of the control signals and the data signals; comparingthe determined SNR to the modified one or more SNR threshold values todetermine whether the radio link is in-sync or out-of-sync and whetherradio link failure has occurred.

According to some embodiments, the characteristics of decodingperformance for one or more of the control signals and the data signalscomprise at least a power boosting factor used by the base station toboost transmit power of one or more of the control signals or the datasignals relative to the reference signals.

According to some embodiments, an indication of a value of the powerboosting factor is received from the base station by the wirelessdevice.

According to some embodiments, a value of the power boosting factor isinferred by the wireless device based on measured characteristics ofreceived control and/or data signals or is a predetermined value knownby the wireless device a priori.

According to some embodiments, performing radio link monitoring of theradio link comprises: adjusting one or more out-of-sync or in-synccounters and/or timers based at least in part on the characteristics ofdecoding performance for one or more of the control signals and the datasignals.

According to some embodiments, the method further comprises: estimatinga decoding success rate for the control signals over a radio linkmonitoring window; and determining a modulation and coding scheme (MCS)for the data signals; wherein performing radio link monitoring of theradio link is further based at least in part on the estimated decodingsuccess rate and the determined MCS.

According to some embodiments, estimating a decoding success rate forthe control signals over a radio link monitoring window comprisesdetermining that one or more control signals intended for the wirelessdevice were not detected based on one or more of: symbol energy metricsand tail biting properties of convolutional codes of the controlsignals; a semi-persistent-scheduling grant; traffic to pilot ratio(TPR) estimation; a redundancy version (RV) sequence pattern used inconjunction with data signals transmitted by the base station using ahybrid automatic repeat request (HARD) retransmission technique; ordownlink assignment index (DAI) information.

Yet another set of embodiments may include a wireless device,comprising: an antenna; a radio coupled to the antenna; and a processingelement coupled to the radio; wherein the wireless device is configuredto establish a radio link with a cellular base station according to aradio access technology, wherein the base station provides referencesignals, control signals, and data signals to the wireless device viathe radio link; and perform radio link monitoring of the radio linkbased at least in part on the reference signals and further based atleast in part on characteristics of decoding performance for one or moreof the control signals and the data signals.

According to some embodiments, the radio link monitoring comprisesdetermining whether the radio link is in-sync or out-of-sync for each ofa plurality of monitoring windows, wherein the characteristics ofdecoding performance for one or more of the control signals and the datasignals are used to perform radio link monitoring based at least in parton determining that the radio link has been out-of-sync for at least anout-of-sync threshold number of monitoring windows.

According to some embodiments, at a later time, the wireless device isconfigured to: determine that the radio link has been in-sync for atleast an in-sync threshold number of monitoring windows; wherein thecharacteristics of decoding performance for one or more of the controlsignals and the data signals are not used to perform radio linkmonitoring at the later time based at least in part on determining thatthe radio link has been in-sync for at least the in-sync thresholdnumber of monitoring windows.

According to some embodiments, to perform radio link monitoring of theradio link based at least in part on the reference signals and furtherbased at least in part on characteristics of decoding performance forone or more of the control signals and the data signals, the wirelessdevice is further configured to: determine a signal quality metric valuefor the reference signals provided by the base station via the radiolink during a monitoring window; determine a modification to at leastone signal quality metric threshold value based on the characteristicsof decoding performance for one or more of the control signals and thedata signals received during the monitoring window to produce at leastone modified signal quality metric threshold value for the monitoringwindow; and compare the signal quality metric value to the at least onemodified signal quality metric threshold value to determine whether theradio link is in-sync or out-of-sync during the monitoring window.

According to some embodiments, to perform radio link monitoring of theradio link, the wireless device is further configured to: adjust one ormore of the following based at least in part on the characteristics ofdecoding performance for one or more of the control signals and the datasignals: an out-of-sync counter; an in-sync counter; or an out-of-synctimer.

A further exemplary set of embodiments may include a non-transitorycomputer accessible memory medium comprising program instructions which,when executed at a device, cause the device to implement any or allparts of any of the preceding examples.

A still further exemplary set of embodiments may include a computerprogram comprising instructions for performing any or all parts of anyof the preceding examples.

Yet another exemplary set of embodiments may include an apparatuscomprising means for performing any or all of the elements of any of thepreceding examples.

In addition to the above-described exemplary embodiments, furtherembodiments of the present disclosure may be realized in any of variousforms. For example some embodiments may be realized as acomputer-implemented method, a computer-readable memory medium, or acomputer system. Other embodiments may be realized using one or morecustom-designed hardware devices such as ASICs. Still other embodimentsmay be realized using one or more programmable hardware elements such asFPGAs.

In some embodiments, a non-transitory computer-readable memory mediummay be configured so that it stores program instructions and/or data,where the program instructions, if executed by a computer system, causethe computer system to perform a method, e.g., any of a methodembodiments described herein, or, any combination of the methodembodiments described herein, or, any subset of any of the methodembodiments described herein, or, any combination of such subsets.

In some embodiments, a device (e.g., a UE 106 or 107) may be configuredto include a processor (or a set of processors) and a memory medium,where the memory medium stores program instructions, where the processoris configured to read and execute the program instructions from thememory medium, where the program instructions are executable toimplement any of the various method embodiments described herein (or,any combination of the method embodiments described herein, or, anysubset of any of the method embodiments described herein, or, anycombination of such subsets). The device may be realized in any ofvarious forms.

Although the embodiments above have been described in considerabledetail, numerous variations and modifications will become apparent tothose skilled in the art once the above disclosure is fully appreciated.It is intended that the following claims be interpreted to embrace allsuch variations and modifications.

What is claimed is:
 1. A wireless device, comprising: an antenna; aradio coupled to the antenna; and a processing element coupled to theradio, wherein the processing element is configured to cause thewireless device to: establish a radio link with a cellular base stationaccording to a radio access technology, wherein the base stationprovides reference signals, control signals, and data signals to thewireless device via the radio link; perform radio link monitoring of theradio link based at least in part on the reference signals; anddetermine whether to perform radio link monitoring of the radio linkfurther based at least in part on characteristics of decodingperformance for one or more of the control signals and the data signals,wherein performing radio link monitoring of the radio link is furtherbased at least in part on the characteristics of decoding performancewhen it is determined to perform radio link monitoring of the radio linkfurther based at least in part on the characteristics of decodingperformance, and wherein the characteristics of decoding performancecomprise at least a power boosting factor used by the base station toboost transmit power of one or more of the control signals or the datasignals relative to the reference signals.
 2. The wireless device ofclaim 1, wherein determining whether to perform radio link monitoring ofthe radio link based at least in part on the characteristics of decodingperformance comprises determining whether the radio link is in-sync orout-of-sync and determining whether radio link failure has occurred. 3.The wireless device of claim 1, wherein determining whether to performradio link monitoring of the radio link further based at least in parton characteristics of decoding performance for one or more of thecontrol signals and the data signals is based at least in part onwhether a number of out-of-sync instances reaches an out-of-syncthreshold.
 4. The wireless device of claim 1, wherein performing radiolink monitoring of the radio link comprises, when it is determined notto perform radio link monitoring of the radio link further based atleast in part on the characteristics of decoding performance:determining a signal to noise ratio (SNR) of the reference signalsduring a monitoring window; comparing the SNR of the reference signalsduring the monitoring window to one or more SNR threshold values todetermine whether the radio link is in-sync or out-of-sync during themonitoring window; and determining whether radio link failure hasoccurred based at least in part on whether the radio link is in-sync orout-of-sync during the monitoring window, wherein performing radio linkmonitoring of the radio link comprises, when it is determined to performradio link monitoring of the radio link further based at least in parton characteristics of decoding performance for one or more of thecontrol signals and the data signals: determining a signal to noiseratio (SNR) of the reference signals during a monitoring window;determining a modification to one or more SNR threshold values based onthe characteristics of decoding performance for one or more of thecontrol signals and the data signals during the monitoring window;comparing the SNR of the reference signals during the monitoring windowto the one or more modified SNR threshold values to determine whetherthe radio link is in-sync or out-of-sync during the monitoring window;and determining whether radio link failure has occurred based at leastin part on whether the radio link is in-sync or out-of-sync during themonitoring window.
 5. The wireless device of claim 1, wherein theprocessing element is further configured to cause the wireless deviceto, when performing radio link monitoring of the radio link based atleast in part on the reference signals and further based at least inpart on characteristics of decoding performance for one or more of thecontrol signals and the data signals: reset one or more of anout-of-sync counter or an out-of-sync timer when decoding performancefor one or more of the control signals and the data signals during amonitoring window meets one or more resetting criteria.
 6. The wirelessdevice of claim 1, wherein an indication of a value of the powerboosting factor is received from the base station by the wirelessdevice.
 7. The wireless device of claim 1, wherein a value of the powerboosting factor is inferred by the wireless device based on measuredcharacteristics of received control and/or data signals or is apredetermined value known by the wireless device prior to establishingthe radio link with the cellular base station.
 8. An apparatus,comprising: a processing element configured to cause a wireless deviceto: establish a radio link with a cellular base station according to aradio access technology, wherein the base station provides referencesignals, control signals, and data signals to the wireless device viathe radio link; estimate a decoding success rate for the control signalsover a radio link monitoring window; and determine a modulation andcoding scheme (MCS) for the data signals; and perform radio linkmonitoring of the radio link using characteristics of decodingperformance for one or more of the control signals and the data signals,wherein performing radio link monitoring of the radio link comprisesdetermining whether the radio link is in-sync or out-of-sync anddetermining whether radio link failure has occurred, and whereinperforming radio link monitoring of the radio link is further based atleast in part on the estimated decoding success rate and the determinedMCS.
 9. The apparatus of claim 8, wherein radio link monitoring of theradio link is further based at least in part on the reference signals.10. The apparatus of claim 8, wherein performing radio link monitoringof the radio link comprises: determining a signal to noise ratio (SNR)of cell-specific reference signals (CRS) provided by the base stationvia the radio link; determining a modification to each of one or moreSNR threshold values based on the characteristics of decodingperformance for one or more of the control signals and the data signals;comparing the determined SNR to the modified one or more SNR thresholdvalues to determine whether the radio link is in-sync or out-of-sync andwhether radio link failure has occurred.
 11. The apparatus of claim 8,wherein the characteristics of decoding performance for one or more ofthe control signals and the data signals comprise at least a powerboosting factor used by the base station to boost transmit power of oneor more of the control signals or the data signals relative to thereference signals.
 12. The apparatus of claim 11, wherein an indicationof a value of the power boosting factor is received from the basestation by the wireless device.
 13. The apparatus of claim 11, wherein avalue of the power boosting factor is inferred by the wireless devicebased on measured characteristics of received control and/or datasignals or is a predetermined value known by the wireless device priorto establishing the radio link with the cellular base station.
 14. Theapparatus of claim 8, wherein performing radio link monitoring of theradio link comprises: adjusting one or more out-of-sync or in-synccounters and/or timers based at least in part on the characteristics ofdecoding performance for one or more of the control signals and the datasignals.
 15. The apparatus of claim 8, wherein estimating a decodingsuccess rate for the control signals over a radio link monitoring windowcomprises determining that one or more control signals intended for thewireless device were not detected based on one or more of: symbol energymetrics and tail biting properties of convolutional codes of the controlsignals; a semi-persistent-scheduling grant; traffic to pilot ratio(TPR) estimation; a redundancy version (RV) sequence pattern used inconjunction with data signals transmitted by the base station using ahybrid automatic repeat request (HARD) retransmission technique; ordownlink assignment index (DAI) information.
 16. An apparatus,comprising: a processing element configured to cause a wireless deviceto: establish a radio link with a cellular base station according to aradio access technology, wherein the base station provides referencesignals, control signals, and data signals to the wireless device viathe radio link; and perform radio link monitoring of the radio linkbased at least in part on the reference signals and further based atleast in part on characteristics of decoding performance for one or moreof the control signals and the data signals, wherein the radio linkmonitoring comprises determining whether the radio link is in-sync orout-of-sync for each of a plurality of monitoring windows, and whereinthe characteristics of decoding performance for one or more of thecontrol signals and the data signals are used to perform radio linkmonitoring based at least in part on determining that the radio link hasbeen out-of-sync for at least an out-of-sync threshold number ofmonitoring windows.
 17. The apparatus of claim 16, wherein, at a latertime, the wireless device is configured to: determine that the radiolink has been in-sync for at least an in-sync threshold number ofmonitoring windows; and wherein the characteristics of decodingperformance for one or more of the control signals and the data signalsare not used to perform radio link monitoring at the later time based atleast in part on determining that the radio link has been in-sync for atleast the in-sync threshold number of monitoring windows.
 18. Theapparatus of claim 16, wherein to perform radio link monitoring of theradio link based at least in part on the reference signals and furtherbased at least in part on characteristics of decoding performance forone or more of the control signals and the data signals, the wirelessdevice is further configured to: determine a signal quality metric valuefor the reference signals provided by the base station via the radiolink during a monitoring window; determine a modification to at leastone signal quality metric threshold value based on the characteristicsof decoding performance for one or more of the control signals and thedata signals received during the monitoring window to produce at leastone modified signal quality metric threshold value for the monitoringwindow; and compare the signal quality metric value to the at least onemodified signal quality metric threshold value to determine whether theradio link is in-sync or out-of-sync during the monitoring window. 19.The apparatus of claim 16, wherein to perform radio link monitoring ofthe radio link, the wireless device is further configured to: adjust oneor more of the following based at least in part on the characteristicsof decoding performance for one or more of the control signals and thedata signals: an out-of-sync counter; an in-sync counter; or anout-of-sync timer.
 20. The apparatus of claim 16, wherein thecharacteristics of decoding performance for one or more of the controlsignals and the data signals comprise at least a power boosting factorused by the base station to boost transmit power of one or more of thecontrol signals or the data signals relative to the reference signals.